Separation of gamma-valerolactone from water



April 4, 1950 G. E. HAM 2,503,200

SEPARATION OF GAMMA-VALEROLACTONE FROM WATER Filed March 25, 1948 f 2 She ets-Sheet 1 Fuauee GEORGE E. HAM INVENTOR.

April 4, 1950 HAM 2,503,200

SEPARATION OF GAMMA-VALEROLACTONE FROM WATER Filed March 25, 1948 2 Sheets-Sheet 2 F GUIZE 2.

WATER eAMMA-vALERoLAc-rou '3 5 -o 7 65 b 0 4 0 75 I l l0 5 iv vkv vvv r vmv v X/WNNWAA/VVVVVKVV 25 AAA/w fiwM/mAM/v GEORGE E. HAMT INVENTOR.

BY QMWW Patented A r. 4, 1950 SEPARATION OF GAMMA -VALERO LACTONE FROM WATER George E. Ham, Dayton, Ohio, assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware 1 Application marcn'zs, 1948, Serial: No. 17,096

3 Claims. (Cl. 260344') This invention relates to a method of separating lactones from water solutions, particu larly water solutions containing relatively small proportions of the lactone. More particularly the invention relates to a method of extractinglactones from completely miscible mixtures of lactones and water.

In the preparation of synthetic fibers from polymers of acrylonitrile,"particularly those of 70 percent or more by weight of acrylonitrile and up to 30 percent of other polymerizable monomers, it is customary to dissolve the polymer in a suitable solvent and to extrude the solution so prepared through an orifice, or a spinnerette comprising a'plurality of orifices, into a medium which removes the solvent and coagulates the polymer as a continuous solid fiber. The said medium must be a liquid which dissolves the polymer solvent butwhich is a nonsolvent for the polymer. Many of the acrylonitrile p'olym'er solvents are water soluble and when these are used the fibers may be extruded into water or an aqueous medium.

In application, Serial No. 351, filed January 2, 1948, by Carroll .A. Hochwalt, now abandoned there are described and claimed methods of preparing synthetic fiber from solutions of polyacrylonitrile and acrylonitrile coploymers in butyrolactone by the aforementioned conventional spinning technique. When the butyrolactone solutions are extruded into water the butyrolactone is dissolved by the water and accumulates in the aqueous bath, from which it must be recovered to effect an economically practicable fiber production method. Similarly when gamma-valerolactone is used as a solvent for copolymers of acryonitrile, methacrylonitrile and vinyl acetate, which method'is described and claimed in application, Serial No. 17,111, filed March 25, 1948 by Carroll A. Hochwalt, now abandoned the gamma-valerolactone must be recovered from the aqueous bath for reuse.

Although the spinning of acrylonitrile polymers and copolymers from solutions in butyrolactone or'gamma-valerolactone may be efiectively accomplished using water as the spinning medium, it is usually more effective to spin the polymer solutions into a medium which reacts chemically with the lactones and thereby more effectively removes solvent from extruded fiber. Methods of this type are described and claimed in copending application, Serial No. 17,112, filed March 25, 1948, by Carroll A. Hochwalt, in which method an aqueous alkaline bath is used which converts the lactones into water soluble salts of the corresponding hydroxy acids. The spent spin-bath solutions containing substantial proortions of the dissolved salts of the hydroxy acids must be processed to recover the lactones. This is accomplished by acidifying the bath with any inexpensive acid, such assulfuric and hydrochloric acid to obtain an aqueous solution of the regenerated lactone.

The purpose of the present invention is to provide a method of separating the gammavalerolactone, butyrolactone, or any other stable lactone having five or six member lactone rings, from the high concentrations of water as occur in th waste water from wet spinning operations. A further purpose of the invention-is to provide a continuous cyclic process of spinning acrylonitrile fibers from lactone solutions with the effective recovery and reuse of the solvent.

It has beenfound that stable lactones havin the structure:

wherein R is a, divalent aliphatic hydrocarbon radical of the group consisting of radicals hav ing three or four carbon atoms between the carbonyl and oxygen radicals, such as gammavalerolactone and butyrolactone, may be conveniently separated from dilute water solutions by extraction with an aromatic hydrocarbon. Suitable hydrocarbons are benzene, toluene and the various isomeric xylenes, of these benzene being the most efiicient and least expensive, is more economically feasible. The aqueous wastes from wetspinning operations involving the use of lactones as solvents will usually contain from 5 to 25 percent by weight of the lactone, the balance being essentially water. After a quantity of the aqueous liquor is mixed with a small proportion of an aromatic hydrocarbon, for example from'5 to 25 percent by weight, the mixture will separate into two distinct liquid phases, of which the upper phase will be the hydrocarbon containing a high proportion ofthe lactone. The lower aqueous'phase, which contains a much'smaller proportion of the lactone, may again be treated with a further quantity of the hydrocarbon and another substantial separation of the lactone thereby effected. Obviously as many extractions may be used as desired to effect an economical operation. Continuous countercurrent extracting methods are also adaptable in apparatus conventionally used to effect liquid extractions.

Further details of the method of practicing ically that mixtures of large proportions of I gamma-valerolactone and small proportions of both water and benzene are entirely miscible. That is, with respect to proportions represented by the area above and to the right of the curved line DE, only a single liquidphase is present. Although water lactone mixtures and benzene lactone mixtures are miscible in all proportions, all three component mixtures represented by the diagram area to the left and below line DE will contain two liquid phases. The, diagram also shows a series of diagonal lines FG, HJ, KL, and MN, which are known as tie lines, the axial interceptsof which represent the distribution of the lactone in the aqueous and hydrocarbon phases. For any mixture of water, gammavalerolactoneand benzene there is a tie line which passes through the point on the diagram representing that composition and has a slope such that the intersections of the line with the base lines of the diagram show the composition of each phase. Compositions which fall between the tie lines drafted on Figure 1, may be determined by interpolation or reasonable extrapolation. It will be readilyapparent from the ternary diagram that the hydrocarbon layers will contain very high proportions of the gamma-valerolam tone from which the pure lactone can be separated by evaporation of the hydrocarbon. Because the hydrocarbons and the lactones form normal distillable mixtures free from azeotropes, rapid and effective separation of the hydrocarbon from the lactone is possible.

Figure 2, shows the ternary system which is involved in the use of toluene as the extractant in place of the benzene. It will be apparent that the gamma-valerolactone may be effectively separated from water by the use of toluene, although the distribution ratio of the gamma-valerolactone in water and toluene is not quite as favorable as in the case of benzene.

Further details of the practice of this invention are set forth with respect to the following example.

. Example An aqueous solution of 20 percent by weight of gamma-valerolactone was mixed with onefifth its weight of benzene. After the two phase .system'rea-ched a state of equilibrium, the two phases were separated. The benzene layer was :fractionated in a distillation column using a 5:l :reflux ratio at atmospheric pressure and virtually complete separation of benzene and gammavalerolactone Was effected. The benzene layer was found to contain.29.7 percent byweight of gamma-valerolactone which was 62.2 percent of 4 the gamma-valerolactone in the aqueous solution. Thus a single extraction with benzene reduced the gamma-valerolactone content of the aqueous solution from percent to 8.5 percent. The gamma-valerolactone recovered was of sufilcient purity (n =l.4=323) to dissolve a copolymer of 84 percent aorylonitrile, :11 percent methacrylonitrile, and 5"percent vinyl acetate. A temperature of 100 C. was used to effect the solution but the resulting solution was stable at room temperature.

When countercurrent extraction apparatus is used substantially complete separation of the lactone from water is possible thereby avoiding th costly evaporation of water. Because of the much higher concentrations of the lactone in the hydrocarbon solutions the evaporation of a much smaller proportion'of the hydrocarbon is relatively less costly.

Although the invention has been described with respect to a specific example showing a single stage extraction, it should be apparent that multiple stage extractions, and especially extractions utilizing countercurrent flow are readily practicable. The scope of the invention is only limited to the extent that the details are incorporated in the following claims.

Iclaim: a

1. A method of separating gamma-valerolactone from aqueous solutions thereof which comprises mixing benzene with the said aqueous solution, in sufficient amount 'to produce two liquid phases, separating the two liquid phases so produced, evaporating thelbenzene from th nonaqueous phase, and recovering the separated gamma-valerolactone.

2. A method of separating gamma-valerolactone from aqueous solutions thereof which comprises mixing toluene with the said aqueous solution, in sufficient amount to produce two liquid phases, separating the two liquid phases so produced, evaporating the toluene from the non-aqueous phase, and recovering the separated gamma-valerolactone. v 3. A method'of. separating gamma valerolactone from aqueous solutions thereof, which comprises mixing the aqueous solution with a hydrocarbon of the group consisting of benzene, toluene and the xylenes, in sufficient amount to product two liquid phases, separating the two liquid phases so produced and evaporating the hydrocarbon from the non-aqueous phase.

GEORGE E. HAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

3. A METHOD OF SEPARATING GAMMA VALEROLACTONE FROM AQUEOUS SOLUTIONS THEREOF, WHICH COMPRISES MIXING THE AQUEOUS SOLUTION WITH A HYDROCARBON OF THE GROUP CONSISTING OF BENZENE, TOLUENE AND THE XYLENES, IN SUFFICIENT AMOUNT TO PRODUCT TWO LIQUID PHASES, SEPARATING THE TWO LIQUID PHASES SO PRODUCED AND EVAPORATING THE HYDROCARBON FROM THE NON-AQUEOUS PHASE. 